( function () {
class AnaglyphEffect {
  constructor(renderer, width = 512, height = 512) {
    // Dubois matrices from https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.7.6968&rep=rep1&type=pdf#page=4
    this.colorMatrixLeft = new THREE.Matrix3().fromArray([0.456100, -0.0400822, -0.0152161, 0.500484, -0.0378246, -0.0205971, 0.176381, -0.0157589, -0.00546856]);
    this.colorMatrixRight = new THREE.Matrix3().fromArray([-0.0434706, 0.378476, -0.0721527, -0.0879388, 0.73364, -0.112961, -0.00155529, -0.0184503, 1.2264]);

    const _camera = new THREE.OrthographicCamera(-1, 1, 1, -1, 0, 1);

    const _scene = new THREE.Scene();

    const _stereo = new THREE.StereoCamera();

    const _params = {
      minFilter: THREE.LinearFilter,
      magFilter: THREE.NearestFilter,
      format: THREE.RGBAFormat
    };

    const _renderTargetL = new THREE.WebGLRenderTarget(width, height, _params);

    const _renderTargetR = new THREE.WebGLRenderTarget(width, height, _params);

    const _material = new THREE.ShaderMaterial({
      uniforms: {
        'mapLeft': {
          value: _renderTargetL.texture
        },
        'mapRight': {
          value: _renderTargetR.texture
        },
        'colorMatrixLeft': {
          value: this.colorMatrixLeft
        },
        'colorMatrixRight': {
          value: this.colorMatrixRight
        }
      },
      vertexShader: ['varying vec2 vUv;', 'void main() {', '	vUv = vec2( uv.x, uv.y );', '	gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );', '}'].join('\n'),
      fragmentShader: ['uniform sampler2D mapLeft;', 'uniform sampler2D mapRight;', 'varying vec2 vUv;', 'uniform mat3 colorMatrixLeft;', 'uniform mat3 colorMatrixRight;', // These functions implement sRGB linearization and gamma correction
      'float lin( float c ) {', '	return c <= 0.04045 ? c * 0.0773993808 :', '			pow( c * 0.9478672986 + 0.0521327014, 2.4 );', '}', 'vec4 lin( vec4 c ) {', '	return vec4( lin( c.r ), lin( c.g ), lin( c.b ), c.a );', '}', 'float dev( float c ) {', '	return c <= 0.0031308 ? c * 12.92', '			: pow( c, 0.41666 ) * 1.055 - 0.055;', '}', 'void main() {', '	vec2 uv = vUv;', '	vec4 colorL = lin( texture2D( mapLeft, uv ) );', '	vec4 colorR = lin( texture2D( mapRight, uv ) );', '	vec3 color = clamp(', '			colorMatrixLeft * colorL.rgb +', '			colorMatrixRight * colorR.rgb, 0., 1. );', '	gl_FragColor = vec4(', '			dev( color.r ), dev( color.g ), dev( color.b ),', '			max( colorL.a, colorR.a ) );', '}'].join('\n')
    });

    const _mesh = new THREE.Mesh(new THREE.PlaneGeometry(2, 2), _material);

    _scene.add(_mesh);

    this.setSize = function (width, height) {
      renderer.setSize(width, height);
      const pixelRatio = renderer.getPixelRatio();

      _renderTargetL.setSize(width * pixelRatio, height * pixelRatio);

      _renderTargetR.setSize(width * pixelRatio, height * pixelRatio);
    };

    this.render = function (scene, camera) {
      const currentRenderTarget = renderer.getRenderTarget();
      scene.updateMatrixWorld();
      if (camera.parent === null) camera.updateMatrixWorld();

      _stereo.update(camera);

      renderer.setRenderTarget(_renderTargetL);
      renderer.clear();
      renderer.render(scene, _stereo.cameraL);
      renderer.setRenderTarget(_renderTargetR);
      renderer.clear();
      renderer.render(scene, _stereo.cameraR);
      renderer.setRenderTarget(null);
      renderer.render(_scene, _camera);
      renderer.setRenderTarget(currentRenderTarget);
    };

    this.dispose = function () {
      if (_renderTargetL) _renderTargetL.dispose();
      if (_renderTargetR) _renderTargetR.dispose();
      if (_mesh) _mesh.geometry.dispose();
      if (_material) _material.dispose();
    };
  }

}

THREE.AnaglyphEffect = AnaglyphEffect;
} )();
